Flapper valve

Abstract

Flapper valves may be provided in fluid transportation systems. The flapper valves comprise a body adapted for assembly into the system. The body comprises a first sub and a second sub which are removably assembled to each other. A passage is defined in the body which extends through the first and second subs. A seat is removably mounted in the passage. The seat is accessible by disassembling the first sub and the second sub. The valve also has a service port. A cap removably closes the port. A flapper is removably a mounted within the service port for pivoting movement between a closed position and an open position. In the closed position the flapper shuts off back flow through the passage. In the open position, the flapper allows fluid flow through the valve. The flapper is accessible by removing the cap from the service port.

Description

FIELD OF THE INVENTION[0001]The present invention relates generally to flapper valves, and especially to flapper check valves for fluid transportation systems conveying fluids under high pressure as are common, for example, in the oil and gas industry.BACKGROUND OF THE INVENTION[0002]Hydrocarbons, such as oil and gas, may be recovered from various types of subsurface geological formations. The formations typically consist of a porous layer, such as limestone and sands, overlaid by a nonporous layer. Hydrocarbons cannot rise through the nonporous layer. Thus, the porous layer forms a reservoir, that is, a volume in which hydrocarbons accumulate. A well is drilled through the earth until the hydrocarbon bearing formation is reached. Hydrocarbons then are able to flow from the porous formation into the well.[0003]In what is perhaps the most basic form of rotary drilling methods, a drill bit is attached to a series of pipe sections referred to as a drill string. The drill string is susp...

AI Technical Summary

Benefits of technology

The invention is about flapper valves for fluid transportation systems. The valves have a body with a passage for fluid to flow through. The body has a first and second sub, which can be assembled together. A seat is mounted in the passage and a flapper is pivotally connected to a bracket. The valves can be used in high-pressure fluid transportation systems. The invention provides various features and combinations of features to overcome shortcomings of the prior art. The technical effects of the invention include improved control of fluid flow, improved reliability, and improved performance under high-pressure conditions.

Problems solved by technology

Hydrocarbons, however, are not always able to flow easily from a formation to a well.

Other formations, however, such as shale rock, limestone, and coal beds, are only minimally porous.

The formation may contain large quantities of hydrocarbons, but production through a conventional well may not be commercially practical because hydrocarbons flow though the formation and collect in the well at very low rates.

Pressure builds rapidly to the point where the formation fails and begins to fracture.

Continued pumping of fluid into the formation will tend to cause the initial fractures to widen and extend further away from the well bore, creating flow paths to the well.

Systems for successfully performing a fracturing operation, therefore, are extensive and complex, as may be appreciated from FIG. 1. FIG. 1 illustrates schematically a common, conventional frac system.

Flow iron components are fabricated from heavy, high tensile steel and are quite rugged.

Once pumping is stopped, however, large quantities of slurry will flow out of the well at rates and pressures at least initially comparable to those used to fracture the well.

Actuating shut off valves, however, may take some time.

Operators also may neglect to open or shut the appropriate valves.

Flow in the opposite, undesired direction, however, will cause the flapper to bear and seal against the seat, shutting off back flow through the valve.

Eventually, however, the flapper and seat can become eroded such that the ability of the valve to check flow in the opposite direction is impaired.

A disadvantage lies in the installation of the seat.

Threaded seats are difficult to align with the flapper, and so typically threaded seats are provided with vertical seat faces.

Pressure fitted seats may be difficult to install and remove.

Flapper valves, like other flow iron components, are fabricated from steel and are quite rugged.

Nevertheless, they can suffer shortened service life or failure due to the harsh conditions to which they are exposed.

Not only are fluids pumped through the system at very high pressure and flow rates, but the fluid is abrasive and corrosive.

Components may suffer relatively rapid erosion.

Any failure of flapper valves on site may interrupt fracturing, potentially reducing its effectiveness and inevitably increasing the amount of time required to complete the operation.

Fracturing a horizontal well, however, may require fracturing in 20 or more zones.

A problem with all flapper valves derives from the fact that they necessarily require an enlarged area within the passage to accommodate installation and operation of the seat and flapper.

The enlarged portion of the passage in turn cause turbulence in fluids flowing through the valve.

Turbulence in the valve not only creates pressure losses in the flowline, but can dramatically increase the rate of erosion in the valve, especially when the fluids are laden with abrasive particulates.

The seat and flapper in particular are highly exposed to turbulence in the valve and its attendant erosion.

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